Smart power integrated circuit technology has evolved to where entire electronic systems are built into a single integrated circuit chip. The single chip combines analog, digital, and power functions to provide system functions. The single chip replaces multiple integrated circuit chips and enables manufacturers to build smaller systems. Applications include systems in the automotive, industrial, telecommunication, and data processing fields. The single chip can be manufactured via a bipolar, complementary metal oxide semiconductor (CMOS), double-diffused metal oxide semiconductor (DMOS) process, referred to as a BCD process.
Typically, smart power electronics are manufactured via either conventional bulk silicon substrates or silicon-on-insulator (SOI) substrates. The SOI substrates contain a buried oxide layer that is about 0.1-1 micrometer (μm) thick and 1-5 μm under the surface of the chip.
Usually, in bulk silicon a p-type substrate is used and an n-plus buried layer is situated between the p-type substrate and an n-type epitaxial layer. The n-plus buried layer is contacted via a sinker diffusion contact. Device isolation is provided via trench isolation regions and the highly doped n-plus buried layer. The trench isolation regions also serve to contact the p-type substrate that would otherwise be floating. Bulk silicon substrates are less expensive than SOI substrates. However, the sinker diffusion contact is expensive and consumes area on the chip. Also, device isolation is not complete such that devices are not completely isolated from one another.
SOI provides complete dielectric isolation of devices that are laterally isolated via trench regions and vertically isolated via the buried oxide layer. However, SOI substrates are expensive in comparison to bulk silicon substrates. In addition, the high thermal resistance of the oxide layer prevents heat from flowing away from the power devices, which can lead to degraded performance of the power devices.
For these and other reasons there is a need for the present invention.